1. Field of the Invention
This invention relates to a surgical stapler for suturing or sewing up a wound or the like.
2. Prior Art
Japanese Laid-Open (Kokai) Patent Application No. 64782/76 (corresponding to U.S. patent application Ser. No. 516,112 filed Oct. 18, 1974), Japanese Patent Publication No. 4535/86 (corresponding to German Patent Application No. 3204522.0 filed Feb. 10, 1982) and Japanese Patent Publication No. 37983/87 (corresponding to U.S. patent application Ser. No. 374,692 filed May 4, 1982) disclose gun-shaped staplers. Such a conventional stapler comprises a body having a grip portion and an elongated portion extending generally perpendicularly from one end of the grip portion. A ram is mounted within the elongated portion so as to be slidable along the length of the elongated portion. A trigger member is movably supported on the grip portion. When the trigger member is urged toward the grip portion, the force thus applied to the trigger member is transmitted to the ram through a force-increasing means mounted within the body, so that the ram advances to cooperate with an anvil, mounted at the distal end of the elongated portion, to deform a staple. Such a conventional stapler is disadvantageous in that it is of a large size and heavy in weight.
Japanese Patent Publication No. 6773/81 corresponding to U.S. patent application Ser. No. 742,843 filed Nov. 18, 1976), Japanese Patent Publication No. 38692/86 (corresponding to U.S. patent application Ser. No. 229,080 filed Jan. 28, 1981) and Japanese Patent Publication No. 36694/87 (corresponding to U.S. patent application Ser. No. 961,740 filed Nov. 17, 1978) disclose staplers which comprise an elongated body and a lever which are pivotally connected together at their distal ends. The distal end of the lever is engaged with a ram. When the lever is urged toward the body while the lever and the body are gripped by the operator, the ram is advanced through the leverage of the lever under a strong force, so that the ram cooperates with an anvil to deform a staple. This type of conventional stapler is also disadvantageous in that it is of a large size and heavy in weight.
A lightweight and small-size stapler is disclosed in Japanese Patent Publication No. 164050/84 (corresponding to U.S. patent application Ser. No. 470,066 filed Feb. 28, 1983). This conventional stapler comprises an elongated body, and a drive member (which corresponds to the lever of the above-mentioned conventional staplers) which is foldable at its mid portion so as to serve as a toggle joint mechanism. The proximal end portion of the drive member is pivotally supported by the proximal end portion of the body, and the distal end portion of the drive member is pivotally connected to a ram which is supported by the distal end portion of the body so as to be slidable along the length of the body. When the drive member is in its inoperative condition, that is, in its non-pressed condition, the drive member is held in its folded condition, with its mid portion spaced away from the body. When the mid portion of the drive member is urged toward the body by the thumb of the operator, with the index finger held against the staple body, the drive member is extended from its folded condition. As a result, the distal end of the drive member advances, so that the ram also advance to deform a staple. Since the foldable mid portion of the drive member is supported by the thumb, the stapler can not be supported by the operator in a stable manner. In addition, the staple-deforming position is considerably spaced away forwardly from the pressing force-applying position (i.e., the manipulating position), and therefore when the pressing force is applied to the drive member, the staple-deforming position may be varied.
Japanese Patent Publication No. 46854/82 (corresponding to U.S. patent application Ser. No. 899,350 filed Apr. 24, 1978 and Ser. No. 26,071 filed Apr. 3, 1979) discloses a stapler which is similar to the stapler described in the above-mentioned Japanese Patent Publication No. 164050/84 and has the same drawbacks.
A lightweight and small-size stapler is also disclosed in Japanese Laid-Open Patent Application No. 82842/84 (corresponding to U.S. patent application Ser. No. 425,542 filed Sept. 28, 1982). In this conventional stapler, a pair of levers are pivotally connected at their proximal ends to the proximal end portion of a body, and a pair of stapleforming elements are pivotally mounted on the distal end portion of the body. The distal ends of the levers are held in contact with the staple-forming elements. When the distal end portions of the pair of levers are pressed or urged by the thumb and the index finger, respectively, the staple-forming elements are pivotally moved at their one ends, so that a staple is deformed by the other ends of the staple-forming elements. This conventional stapler has no function of increasing the force applied by the operator. Therefore, this stapler is disadvantageous in that the operator is required to exert a considerable force to operate the stapler. This conventional stapler employs the staple-forming elements pivotally mounted on the body, instead of a linearly movable ram, and in this respect this stapler is different in basic construction from the stapler of the present invention.